252 GENERAL ANATOMY. 



some parts, these terminations, and especially the radicles of 

 the veins, are larger, and possess an erectile power, which 

 renders them susceptible of experiencing a more or less consi- 

 derable expansion. Finally, in some others, the terminations 

 of the vessels constitute, by their intermixture, and their com- 

 munication, ganglions or particular vascular enlargements. 



I. OF THE CAPILLARY VESSELS. 



375. The capillary or microscopic vessels,* vasa capilla- 

 ria, thus called in consequence of their tenuity, are much 

 finer than hairs, and can not be perceived with the naked eye; 

 although the radicles of the lymphatic vessels participate in 

 this characteristic, nevertheless, it is especially the sanguineous 

 capillary vessels that we shall treat of in this place. 



376. The ancients, who were ignorant of the art of inject- 

 ing vessels, and that of magnifying objects by the help of op- 

 tical instruments, were not acquainted with the extreme vessels. 

 They believed there was between the last ramifications of the 

 arteries and the first of the veins, an extravasated, spongy and 

 sanguineous substance, called parenchyma by Erasistratus, 

 haimalope by Araeteus, and of which they believed the viscera 

 were especially formed. This opinion, on the termination of 

 the vessels, was adopted almost unanimously by all the ana- 

 tomists, till the period of the discovery of the circulation of 

 the blood, and since that time, by a considerable number of 

 anatomists down to the present day. 



The injections of Ent,t however, by demonstrating the di- 

 rect passage, and without the extravasation of the injected li- 

 quid, from the arteries into the veins; the microscopical ob- 

 servations of Malpighi,J and of Leuwenhoeck, made on the 

 transparent parts of reptiles, fishes, and even of bats, in which 

 the blood is seen passing directly from the arteries into the 

 veins; experiments and observations, repeated since a great 



* Prochaska, de vasis sanguin. capill.; in op. cil. 



f Apologia pro circulat. sanguin. ; in op. Leidae, 1687. 



} De pulmonibusy Epist. ii. in oper. omn. 



Exp, el contemp* arcan. natur. detect. Epist. 65, 67, &c. 



